Composite electric cable



July 9, 1940. .1 wl EDWARDS A 2,207,090

' il( owneog- Pieniedinlyo, 194.0

UNITED s'riirlszs PATENT oF-FicE- CoMPosrrE ELECTRIC CABLE Irving W. Edwards, Detroit, Mich.

Application March 26, 193s, Serial No. 198,312 1 Claim. (ci. 1744128) to t the center wire and their outside surfaces shaped to cooperatively provide a substantially cylindrical cable exterior. This center wire can 15 be made of. galvanized steel and the other wires made of copper, this arrangement shielding the galvanized surface of the steel wire against mechanical injury.

Specic examples 'of the above are illustrated by the accompanying drawing, in which Figure 1 is a cross-section of one example; Figure 2 is a cross-section of another example; and, Figure 3 is a. cross-section of still another example.

More specifically, the above show a cylindrical steel wire I that is galvanized to protect it against corrosion, and two copper wires 2 helically laid over this wire I. 'I'he wires 2 have their inside surfaces shaped, as at 3, to t the center Wire I and their outside surfaces shaped semi-cylin- 30 ldrically to cooperativelyprovide a substantially cylindrical cable exterior. 'I'he wire I should have suicient cross-section to support the wires 2 and the latter should have suicient crosssection to carry the electric'power for which the 35 cable is designed. The wires 2- are retained on the Wire I by reason of their being formed Ato the helical congurations they acquire when helically laid over the center wire.

In Figure 2 a twisted fiat strip 4 of galvanized steel takes the place of the round wire I of 'the rst example, the copper Wires 5 being of semicylindrical form and helically laid over the twisted strip 4. The twist f the steel strip and the helical lay of the semi-cylindrical copper wires preserve the cable integrity.

The third example, shown by Figure 3, has grooves 6 formed in the at faces of semi-cylindrical copper wires 5a, the latter being laid in tight contact with a galvanized steel iiat strip 4' 10Q y having ridges 1 ttingin the' grooves 6. 'I'hese grooves should beslightly deeper than the ridges are high to assure the at faces of the wires rmly engaging'the strip. Otherwise, this example is the same as the others. y

A further feature of the invention consists in making or processing the various wires so that they all have physical characteristics providing the same percentages of elongation regardless of their differences respecting elastic limits and tensile strengths. An exemplary way of accomplishing this is by giving a lesser 'number' of cold -drawing drafts to thev hard drawn copper wire relatively softer metal but greater electrical conduotivity helically and interlockingly laid over said strip,. said strip being twisted about its axis.

IRVING w. EDWARDS. 

